Battery Basics for Beginners Wiki [Serious]

Venom121212 · December 2, 2019, 3:21pm

I see the same question being asked by many newcomers here so I would like to shed some BASIC info on batteries used in esk8, notation, configuration, ratings, etc.

Battery Notation

Common battery notation you keep seeing or will see is a (XX)s(YY)p battery with (ZZ) cells:

XX is the number of cells you have in series ( s ) type connection.
YY is the number of cells you have in parallel ( p ) type connection.
ZZ is the actual battery cell type used. At the time this article was written, Samsung 30q was by far the most common here. You will also see 18650, 21700, etc mentioned a lot. That is just the physical dimension of the battery cell, nothing to do with chemistry. An 18650 is a battery 18mm wide by 65.0 mm long. Panasonic, Sony, LG, etc all make 18650 cells. They also make other size cells like the 20700. Can you guess what size that is?

Battery Configuration

Series

When you add cells in series, it adds to the total voltage available to your system.

ex. 30Q cells are 4.2V fully charged,

Ie. 10s is 42V, 12s is 50.4V, 100s is 420V etc.

Parallel

When you add them in parallel, it keeps the voltage the same but adds to the capacity (measured in Ah or more commony mAh).

30Q cells are 3 Ah each (or 3000 mAh if you prefer).

Ie. 4p is 12 Ah (12000 mAh), 10p is 30 Ah, etc.

Very very basically, increasing series adds speed, increasing parallel adds range.
This is assuming you keep all other parts/conditions the same.

Battery Chemistry / Cell Type

If you use the esk8 calculator to design your build on paper before going shopping (highly recommended), you’ll notice there are a number of options in the Cell Type drop-down:

Lithium-Ion Polymer (Li-polymer / LiPo) pouch packs

Lithium-Ion (Li-Ion) cylinder cells

Lithium Iron Phosphate (LiFePo4)

Lithium Titanate (Li2TiO3 / Li4Ti5O12 / LTO)

Lead Acid

Nickel Metal Hydride (Ni-MH)

In 99% of cases, the question to answer is which lithium based battery is best for your use: LiPo or Li-Ion (sometimes LiFePo)?

Some of the following information may be a bit in depth, but beginners will understand more as they read more. Hopefully this is a good reference that can be improved by the community and updated over time. Battery technology develops extremely rapidly, and some of this information will likely be out of date in only a few years.

Common Cell/Pouch Type Info

LiPo

LiPo (typically LCO chemistry, 3.7V nom, 4.2 - 3.6v safe range, polymer gel electrolyte)

General Characteristics:

Cycle_Life: Poor (50-300 charge cycles)
Energy_Density (Specific Energy): Good (100–200 Wh/kg) - Heavier for a given capacity than li-ion / roughly 2x the weight for the same range
Discharge_Rate: Excellent - Highest discharge rates / C rate (“punchy”). Can get much higher discharge on smaller packs if not concerned about range. (10-25C actual / 200A+)
Charge_Rate: Average (1C typical, 3C maximum)
Voltage_Curve: Good - Flatter curve / minimal voltage sag / maintain a higher voltage under load for longer
Cost: Average. Easy to purchase, widely available
Quality: Average - more prone to swings in manufacturing quality, dimensions, and weight
Safety: Poor - Most sensitive to piercing / blunt damage / thermal runaway. Requires hard case for safety. Easily damaged by discharging too far (will unbalance rapidly below 3.6V.
Operating_Temperature: Average, 5 to 50°C charge (damage will occur if charging at over 60°C)
Aging: Poor- easily damaged if left above recommended storage charge for '3+ months
Packaging: pouch packs come in compact ‘bricks’ of varying sizes, encased in a semi-flexible shell. No standard size exists. Easy to replace / swap / carry extra backups, but added complexity of multiple battery packs.
Cell_Balancing: Requires a BMS or balance charger to eliminate state of charge (SOC) mismatch. 
Note: Inaccurate manufacturer C rating is very common (typically around 2-3x exaggerated)
Examples: Gens Tattu, Turnigy Nano-Tech, Turnigy Graphene, Venom, MaxAmps

Read the more detailed lipo thread here: thinking about going lipo
Read the Tattu lipo thread here: Does anyone have experience with Tattu lipo batteries?

Lipos are safe if you maintain them well. If not, they can puff and cause fires. A lithium ion (cylinder) battery pack like discussed below can still burst into flames if you wire it wrong or don’t protect it but are generally safer and easier for beginners. They can give slightly more voltage (power) but also sag faster.

Li-Ion

Li-Ion (typically NMC/NCA chemistry, 3.6V nom, 4.2V - 3.2V safe range, liquid electrolyte)

General Characteristics:

Cycle_Life: Good (1000-2000 charge cycles)
Energy_Density (Specific Energy): Excellent (160–260 Wh/kg) lighter for a given capacity 
Discharge_Rate: Good (250-430 W/kg) - CDR largely depends on cell and manufacturer (15-35A continuous typical)
Charge_Rate: Average (1C typical, 4C maximum)
Voltage_Curve: Average - Depending on cell, can have significant voltage sag in the last half of the discharge (voltage curve)
Cost: High - significant upfront cost includes individual cells plus the materials and labor to build a finished battery pack with BMS electronics, although individual cell prices have steadily decreased over time.
Quality: Excellent - Extremely tight manufacturing tolerances by large global brands ensure high quality cells. Tend to be higher quality packs than LiPo when assembled by a quality builder
Safety: Average - sensitive to physical damage and short circuiting. Requires hard case for safety.
Operating_Temperature: Good, 0 to 60°C charge, -40 to 60°C discharge
Aging: 0.35% - 2.5% / month. Good - better at sitting for long periods of time unused.
Packaging: cells come in cylindrical steel canisters of precise dimensions, with overpressure vents (most common: 18650 = 18mm dia x 65mm L, 21700 = 21mm dia x 70mm L)
Cell_Balancing: Requires a BMS to keep cells balanced
Note: Tend to be over the limit for air flight (99 Whr), aka cannot travel with an assembled pack.
Examples: Molicel P26A and P42A, Sony Murata VTC5D, VTC5A, and VTC6, Samsung 30Q, 30T, and 40T, LG HG2 and HG6, Sanyo NCR2070C and NCR20700A

Example discharge curve:

Read the P42A discussion thread here: Molicel P42A cell discussion

LiFePo4

LiFePo4 (3.2V nom, 3.65V - 2.5V range)

General Characteristics:

Cycle_Life: Excellent (2000-5000 charge cycles)
Energy_Density (Specific Energy): Poor (90-130 Wh/Kg) / poor range/weight
Discharge_Rate: Excellent - 25C / 30A+ continuous
Charge_Rate: Excellent (4C+) fast charge is proven safe.
Voltage_Curve: Excellent (flat) - provides the same voltage across almost the entirety of discharge
Cost: Low
Quality: Excellent - Extremely tight manufacturing tolerances by large global brands ensure high quality cells. Tend to be higher quality packs than LiPo when assembled by a quality builder
Safety: Excellent, stable chemistry - the cathode material will not burn and is not prone to thermal runaway (fire). One of the safest chemistries.
Operating_Temperature: Good, 0 to 55°C charge, -30 to 55°C discharge
Aging: ≤ 6% self-discharge. More tolerant to being left at full charge voltage. Higher self-discharge rate than other chemistries. 10 year shelf life.
Packaging: cells come in all forms including cylinders, pouches, and prismatic packs.
Cell_Balancing: Requires a BMS to keep cells balanced
Examples: A123 ANR26650M1B

Read the A123 thread here: A123 LiFePO4 Cells - the iron man’s battery

LTO

LTO (2.4V nom, 2.8V - 1.5V range)

General Characteristics:

Cycle_Life: Excellent (3000-7000 charge cycles)
Energy_Density (Specific Energy): Bad (60-110 Wh/kg)
Discharge_Rate: Excellent (5C typical, 30C+ maximum)
Charge_Rate: Excellent (1C typical, 20C+ maximum)
Voltage_Curve: Good
Cost: High?
Quality: 
Safety: Excellent - One of the safest chemistries.
Operating_Temperature: Excellent, -10 to 40°C charge, -30 to 75°C discharge
Aging: ≤ 5% self-discharge / month.. >10 years shelf life.
Packaging:
Cell_Balancing: 
Examples:

Voltage Discharge curve:

Lead Acid (SLA)

Lead Acid (2.0V nom, 2.3V - 1.8V range)

General Characteristics:

Cycle_Life: Poor (200-350 charge cycles)
Energy_Density (Specific Energy): The Worst (30-40 Wh/kg)
Discharge_Rate: Good (180 W/kg), 1C - 3C 
Charge_Rate: Bad (≤0.2C)
Voltage_Curve: 
Cost: Low
Quality: High, simple to manufacture
Safety: Good. Although environmentally unfriendly
Operating_Temperature:  -40 - 50°C. Good low and high temp performance.
Aging: 3-20% / month. Slight memory effect.
Packaging:
Cell_Balancing: 
Examples: automotive starter batteries

Ni-MH

Ni-MH (1.2V nom, 1.4V - 1.0V range)

General Characteristics:

Cycle_Life: Poor (~500 charge cycles)
Energy_Density (Specific Energy): Bad (60-120 Wh/kg)
Discharge_Rate:
Charge_Rate: Excellent - only battery that can be ultra-fast charged with little stress
Voltage_Curve: Excellent  - 'low internal resistance allows cells to deliver a nearly constant voltage until they are almost completely discharged.
Cost: Low
Quality: 
Safety: Good. Requires complex charge algorithm, sensitive to overcharge.
Operating_Temperature: -20 - 50 °C. 
Aging: '1-4% self-discharge. 
Packaging -
Cell_Balancing -
Note - Similar to NiCd, but less toxic. Constitute less than 3% of the battery market.
Examples: Eneloop rechargeable NiMH

Battery Cell Ratings

Yes, voltage and capacity (those mAh numbers) matter very much. Remember the examples above with series vs parallel?

25r cells are 2500 mAh cells and sag faster than 30q
30q cells are 3000 mAh cells - comparative example
40t cells are 4000 mAh cells and sags less than 30q

25r is what many prebuilts used to use and were fine. They just won’t carry you very long. Most newcomers I saw when I first joined were upgrading their prebuilt batteries with 30q packs. Currently (as of 12/30/21), the Molicel P42a is the cell of choice for power discharge, high charge rate, and all around solid performance.

@Battery_Mooch is a gentleman and a scholar and also conducts professional cell discharge tests that analyze cell performance under various conditions. If you ever want no BS, solid rating values for cells, search “Mooch insert cell type here” and you should find his results. Mooch, if you have a preferred link you’d like me to drop, Lmk and I’ll fix or adjust the wiki yourself

[Mooch’s response] Thank you @Venom121212 for your kind words!
All my test results and tables can be found here: https://www.e-cigarette-forum.com/blogs/mooch.256958/
While I post some content here I also post to my Mooch Facebook page.

You can not mix cell types. Also don’t mix cells of different age (how many times they’ve been used/charged - called cycles). I don’t want to hear any of that “well technically you can if…” talk. This is a battery basics thread!

Each cell also has a listed amp draw rating. The aforementioned Mooch finds reliable discharge and capacity ratings so that we don’t kill our packs faster than we should.

Example: 30q cells are rated at 15A discharge by Samsung, 20A by Mooch (as long as they don’t overheat!)

Your battery’s total available amp discharge is your cell type’s individual amp draw times your number of parallel groups.

I.e.

A 10s5p of 30q cells will have a max battery amp draw of 100A (20A per cell * 5 parallel groups)

Notice a 12s5p will still have the same max battery amp limit. This is where people will use larger cells to have higher available battery discharges without as many p groups. But… the cells are also physically bigger so factor that in as well.

ESC - After the Battery Upgrade

Your motors are dumb devices. They will happily take whatever your battery sends at them even if it melts them into oblivion. This is where your electronic speed controller (ESC) comes in. It sets the limits of amps (and tons of other things) going to your motors using complex maths I won’t get into. As long as your ESC can handle the voltage rating of your new battery and you stay within its acceptable operating range, you’re good to go. You will find this in the esc specs.

BMS and Charging

It stands for battery management system (BMS). It is wired to your battery and keeps the charge even across all of your parallel groups so your battery doesn’t get unbalanced and have problems.

Charging should be done through the bms to prevent overcharging of individual parallel groups. If the pack is unbalanced after discharging, some of the groups can reach their maximum voltage before others and before the charger would reach its cut off voltage. The bms monitors the individual cell voltages and cuts off charging if any one parallel cell group exceeds its maximum allowable voltage preventing damage and or fires

You can charge your pack at different rates as long as they match your pack’s voltage. The charger will be rated in amps to let you know how quickly it will charge your pack. Might as well charge as quickly as possible right? Eh not so much. Charging too quickly is bad for cells and will shorten their lifespan. Charging slowly is best for your pack but worst for riding your esk8 around aot.

Here is a conservative charge rate formula that isn’t painfully slow either:

[# of parallel groups] * [cell type mAh rating / 3000]

For a 10s5p 30q pack (30q cells rated at 3000 mAh):

[5] * [3000/3000] = 5A charge rate.

Again, you can certainly charge faster or slower than that, this is just my personal recommendation.

Do not ever let your battery pack drain below recommended levels! For this reason, many bms and escs have a hard voltage cutoff where your board will cut all acceleration when too low (cutoff end). You see this happening most going up hills as this draws more power. Most escs used here take it a step further and implement a soft cutoff where, instead of throwing you on your face at a low voltage level, it will slow your board down gradually going to that point (cutoff start). Almost like you’re wounded and limping home to your charger. This brings up the next question, what is a safe discharged rating?

Battery Cutoff Settings

Read the ongoing thread: ESC Battery cutoff settings - #6 by b264

12S lipo (50.4V charge)
cutoff start 45.24V
cutoff end 44.52V

12S li-ion; super-conservative (50.4V charge)
cutoff start 43.2V
cutoff end 40.8V

12S li-ion; conservative (50.4V charge)
cutoff start 42V
cutoff end 38.4V

12S li-ion; aggressive (50.4V charge)
cutoff start 38.4 - 39.6V
cutoff end 36V

12S li-ion; max-range (50.4V charge)
cutoff start 43.2V
cutoff end 36V

Please keep comments to basic-moderate battery related questions. All advanced battery construction questions should be posted in the battery builders club thread and ONLY AFTER READING THE WHOLE THREAD please.

More general introduction guide here: Wiki for new users [Help Wanted (Example part list, FAQ)]

Welcome to Esk8!

akhlut · December 2, 2019, 3:31pm

This needs to be the beginnings of an article for ESK8.news

Venom121212 · December 2, 2019, 3:37pm

I’m open to revising and clarifying if anyone has suggestions.

akhlut · December 2, 2019, 3:50pm

Deffo talk about cell charge and discharge rates

Skatardude10 · December 2, 2019, 3:59pm

I would disagree with this statement. I would say you should not mix cell types, unless you know exactly what you are doing and why. This is probably getting more into advanced territory, and you are (99.9% correct from a beginner perspective) but I’ll expound on what I know and correct me if I am wrong for some context on why you should not mix types and why someone would:

Put as simply as possible, IF you are mixing cell types, you shouldn’t be pulling more amps from each P group / # cells in each P group than any individual cell type is capable of handling, while taking into account ohms law and each cell types measured internal resistance. Internal resistance is huge when it comes to mixxing cell types, because cells with lower IR will tend to have more amps pulled from them (and may be more than they are capable of providing). The same # of different cell types should be the same across P groups (2x VTC6 + 6x 30Q for each P group- not 3x VTC6 for one group and 1x VTC6 the next). The only time I could see mixing cell types being useful would be for packs that mix high IR high capacity cells with low IR lower capacity cells for P group charging for range and high A output for power… even then it’s kind of dumb, lots of math would need to be done to ensure your pack is safe to pull the amps you need, and since cells vary wildly in specs and lifespan mixed cells would need to be chosen wisely for a pack that is reliable and safe long term. Also, different cells as they age the IR changes at different rates not only cell to cell but differently between types of cells.

So, again imo, cells should not be mixed unless you know exactly what you are doing beforehand and have done the math based off real world measurements to verify your math prior to loading your pack. In the context of new builders, sure it’s safe to say never just go mixing different cell types, ever. Feel free to disagree with me, I’ll hear you out.

Venom121212 · December 2, 2019, 4:11pm

I fully agree and almost added a caveat about this but figured no beginner (target audience) should be assembling their own mismatched packs for safety reason.

Saying you can do it may lead noobs to thinking of it as an easy way to upgrade their board.

Your point is valid and taken. I appreciate your clarifying for readers.

@akhlut I agree. I will mention it here but I also want to expand more on that in a “how do I know what esc settings I should use?” as that is the most common esc related question I see here. I will pm a few of you gathering info.

akhlut · December 2, 2019, 4:13pm

I’m here to help.

Collating this information is fairly important to new builders.

linsus · December 2, 2019, 4:30pm

Need to visit the topic of internal resistance. Its such a big part its hard to ignore.

(realised this was for beginners)
Maybe a small section after the basics for the extra lesson? Such as degregation, IR, dendrites, temperature dependencies, etc

and maybe most important of all; a source to stated information

Venom121212 · December 2, 2019, 4:36pm

Good idea but as you mentioned, for beginners, I feel that would be better suited to a more advanced battery analysis and comparison thread.

Don’t want to scare away too many newcomers with a wall of charts and graphs.

linsus · December 2, 2019, 4:39pm

Hopefully the DIY:er is familiar enough with what current, voltage and resistance is. But maybe thats too much to ask?
Maybe a disclaimer is in place; do not play with shit if you dont understand it yet?
Small sections of information is enough I think, graphs get boring quick

annihil8ted · December 2, 2019, 7:25pm

This might be a whole can of worms but maybe a small section or note to state what voltage is considered fully discharged.

Venom121212 · December 2, 2019, 7:32pm

Seems like a basic enough point to make. I’ll add it, thanks!

bonesaw · December 2, 2019, 8:59pm

Would appreciate a section on calculating total continuous/peak discharge from P groups & cell specs, and how that impacts how you set your max battery amps on your ESC. Good write up!

Krindor · December 2, 2019, 9:15pm

For series/parallel, both adds range, as to why they both do, probably don’t need to be mentioned in this basics guide.

Rojitor · December 2, 2019, 9:59pm

Constructive criticism: add a brief explanation of C

Skatardude10 · December 2, 2019, 10:26pm

Or just simplify it that total number of cells regardless of configuration determines the total watt hours, or the “size of your gas tank”. 10S5P with 50 cells has a very slightly higher capacity than 12S4P with 48 cells for example…

And if necessary expound upon it by saying it’s your total (nominal) voltage x total Ah per P group. Using the previous example:

10S x 3.6v per cell nominal x 3Ah per cell x 5P per P group = 540 Watt hours
12S x 3.6v x 3Ah x 4P = 518.4 Wh

Skatardude10 · December 2, 2019, 10:28pm

Is it just me or are C ratings totally backwards and unintuitive when you just want to know how many amps your battery can handle? This is a great suggestion.

Krindor · December 2, 2019, 10:31pm

Agreed, Voltage and Ah are already in the text, might as well define Wh.

b264 · December 3, 2019, 12:23am

Thanks for this writeup, Justin

More information about cutoffs can be found over here

b264 · December 3, 2019, 12:26am

This is kind of like soldering on cells. You should never do it. Those that do it, know exactly what they are doing and why, and what damage it can cause, and how to solder in a way that drastically minimizes that. But I would still recommend never doing it. Anyone who knows enough about it to do it, knows they can disregard that advice, because they know enough about it and what’s happening inside the cell.

Yes, this So basically, never do it.